1. Field of the Invention
The present invention relates to a tape recorder, and more particularly, to a driving device for moving a pole base assembly along a deck so as to move a magnetic tape into and out of close contact with a head drum during magnetic tape loading and unloading.
2. Description of the Related Art
Generally, tape recorders such as a video tape recorders (VTR), camcorders, and the like, have deck mechanisms to record and reproduce data as a magnetic tape runs along a predetermined path defined inside the deck.
FIG. 1 illustrates one example of a moving deck 100, which is typically employed in the tape recorder. The deck 100 of the tape recorder includes a pair of pole base assemblies 140, and a driving device for moving the pole base assemblies 140 along a guide rail 130 of the deck 100 during the loading or unloading of the magnetic tape.
Each of the pole base assemblies 140 includes a base member 141 slidably connected with a guide rail 130, a pole member 145 protruding from an upper surface of the base member 141 and/or a roller member 144. While the guide rail 130 is depicted as being integrally formed with the head drum base 120, which is for seating the head drum 110 on the deck 100, many other variations are available for the structure of the guide rail 130, as will be appreciated by one of ordinary skill in the art.
As shown in FIG. 2, the pole base assembly driving device 150 includes first and second loading gears 153a, 153b, and first and second link members 155a, 155b. 
The first and the second loading gears 153a, 153b are disposed on the deck 100 to correspond to the pair of pole base assemblies 140, respectively, and are driven by the force which is transmitted from a loading motor 151 (FIG. 1) via a predetermined gear train including a main gear 152 (FIG. 1).
The first link member 155a is rotatably connected at one of its ends to the base member 141 of the pole base assembly 140. The second link member 155b is rotatably connected at both of its ends to the other end of the first link member 155a and to the loading gears 153a, 153b, respectively. As a result, the pole base assemblies 140 are moved along the guide rail 130 in association with the rotation of the loading gears 153a, 153b. 
In order to ensure stable data recording or reproducing with respect to the magnetic tape (not shown), during the loading of the magnetic tape, the pole base assemblies 140 should be in close contact to the terminal end of the guide rail 130 toward the head drum 110, and should also maintain the close contact stably.
To this end, conventionally, the loading motor 151 has been driven for an extra time after the pole base assemblies 140 have contacted the end of the guide rail 130 toward the head drum 110 so as to rotate the loading gears 153a, 153b for a predetermined rotation angle.
However, this way causes excessive pressure on the link members 155a, 155b when the loading gears 153a, 153b are driven past that the point at which the pole base assemblies 140 have contacted the end of the guide rail 130. Also, as the loading and unloading of the magnetic tape is repeated, such over pressure is repeatedly exerted on the link members 155a, 155b, causing the link members 155a, 155b to break and subsequently, causing the durability of the deck 100 to degrade.
In order to solve the above-mentioned problem, conventionally, the pole base assembly driving device 150 added torsion springs (S) inside the loading gears 153a, 153b, respectively, as shown in FIG. 3. The torsion springs (S) are disposed to surround the axes 153c of the loading gears 153a, 153b. The torsion springs preferably have one end fixed to an inner sidewall of the loading gear 153a, 153b and the other end fixed to the second link member 155b which is pivotally connected to the loading gear 153a, 153b. 
By this structure, as the loading gears 153a, 153b are rotated past the point at which the pole base assemblies 140 are in contact with the end of the guide rail 130 toward the head drum 110, the loading gears 153a, 153b can be elastically rotated with respect to the second link member 155b within the movement range permitted by the torsion springs (S). Accordingly, the pole base assemblies 140 are in close contact with the end of the guide rail 130, and stay in close contact by the recovery force of the torsion springs (S).
Recently, demand for compact-sized tape recorders has been increasing, and accordingly, components of smaller size and less number are required. However, because the conventional tape recorder requires the loading gears 153a, 153b and the second link member 155b to be pivotally connected with the loading gears 153a, 153b, and also requires torsion springs (S) for the loading gears 153a, 153b, the manufacturing process is relatively complicated and lots of components are required for assembly.